I had the same problem with my .45 Evolution engine. It quit when inverted because it got too rich. I took out the original plug and installed an OS Type F plug and and it ran great and the inverted flight problem went away. I also tried a Fox Miracle plug and it runs great with that as well.
ORIGINAL: lrglnman
YA KNOW i HAVE THE SAME PROB WITH THIS MOTOR.UNTIL I GO INVERTED AND IT DEAD STICKS tHE LOW END NEEDS VERY SMALL MOVEMENTS AND IT LOADS UP ON IDLE BUT. i THINK i AM SUCKING AIR SOMEWERE .WHEN I invert the plane , with it at half throttle most of the time the engine dies like it gets too much fuel or goes to rich but in all other bench test I am running at top notch settings. only when I go inverted.